Part 7

In fact, staying indoors is usually the reason why people are sick. They don't go out into the clean fresh air for fear they'll be too cold! It seems a pity we can't just live out of doors all the time. Perhaps we shall some day; for doctors are finding out that fresh outdoor air and good food are the very best medicines known, and the only "Sure Cures." They are pleasant to take, too. Many cities are providing outdoor schools for children who have weak lungs or are not strong in other ways. Perhaps some day all school children will be allowed to study in the open air at least part of every school day.

II. HEARING AND LISTENING

Now you are all ready to go to work. What are you going to work with? Books? pencils? paper? Yes, but you have something better than those and all ready for use. It is that little kit of tools that are sometimes called our "Five Senses." You remember that we have already talked about one of them, the sense of touch in the skin. Now which one are you going to use first this morning? If your teacher talks to you, I hope it will be the one we call the sense of hearing. Suppose we try to find out something about this sense of hearing, and begin with a little experiment.

Take a piece of cork in your hand and lift it up high and then let it drop into a large basin or tub of water. What happens? The cork strikes and then goes bob-bob-bobbing up and down on its own waves. Now watch the little waves all around the cork. Where do they stop? They don't stop until they touch the edge of the pan; and no matter how big the pan is, the waves go on and on until they reach the edge.

We can see these waves of water, and so we easily believe that they are there. Now there are, just as truly, waves of air all around us. We cannot see the waves, because they are too small and roll too quickly. But some of these, when they roll against our ears, make us hear. They make what we call sound. You have heard about sending messages through the air, without telegraph wires. Wireless messages are often sent to ships out in the middle of the ocean. This is done by starting tiny electric waves, which travel through the air much as the waves of water are traveling across the ocean beneath. Of course there must be a machine, called a receiver, to catch the waves and "hear" the message.

Mother Nature has given each of you two very delicate little receivers to catch the sound waves and carry them to your brain. You know what they are--you can name them. But how are these wonderful little machines made?

You have never seen the whole of your ear. The part on the outside of the head, of course, you can easily see and feel. Sometimes you notice a deaf person put his hand behind his ear and press it forward so as to catch the sound waves better. These waves roll in at the little hole you can see, and travel along a short passage till they come to a round drum, a piece of very thin skin stretched tight like a drumhead.

Have you ever beaten a drum with a stick? You felt the drumhead quiver under the blow, did you not? Well, when the sound waves beat against the drum in the ear, it quivers and starts little waves inside the ear. Each little wave in turn beats against a little bone called the hammer; the hammer beats against another called the anvil, and this against a third called the stirrup; and the quiver of the stirrup is passed on to a little window, opening into a little room with a spiral key-board; and from this, the wave travels along a nerve to the brain. As the waves reach the brain, the brain hears. In this way we hear all sorts of sounds, from the tick of a watch to the whistle of a train.

A section through the right ear.]

There is a sensible old saying, "Never put anything smaller than your elbow into the inner part of your ear." Now, of course, you can't put your elbow into such a tiny hole! So the old saying means, never put anything in. The eardrum is very thin and can easily be broken. Even a slap on the ear, or a loud sound too close to it, might crack and spoil the drum and make one deaf.

The outside ear needs careful washing; there are so many little creases that gather dirt and dust. The deep crease behind the ear, too, will become sore if it is not kept clean.

Besides cleaning your ears, you must train them to listen. Some boys and girls hear just a word or two of what is said, and then guess at the rest and think they are listening, or else ask to have it repeated. We should try to hear exactly what is said; and if we listen carefully, it will soon be much easier to understand at once.

Of course, if you really cannot hear, the doctor can tell you what is the matter, and usually can help you very much. Sometimes people become deaf simply because the throat is swollen. Indeed, most deafness comes from colds and catarrhs and other inflammations of the nose and throat. These spread to the ear through a little tube that runs up to the drum cavity from the back of the throat. Sometimes, when you are blowing your nose, you may feel your ear go "pop"; and that means that you have blown air up into the ear through this little tube. Be sure to see a doctor if you don't hear well; and be sure, too, to tell your teacher, so that she may know why it is you do not hear what she says, and ask her to give you a seat near her, so that you can hear.

Then, too, you should learn to notice outdoor sounds--the songs of the birds, the noises that the animals make, the wind in the trees, and the patter of the rain. The old Norsemen have a story that their god Heimdall had such keen ears that he could hear the grass growing in the meadow and the wool growing on the backs of the sheep! Your ears can never be so keen as that; but there are many, many happy outdoor sounds that you should listen for. They will help to make you happy, too.

Careful listening may sometime save your life. You can hear the car or the train coming, and you can learn to tell from which direction a sound comes. You can learn to tell one sound from another in the midst of many sounds. In more ways than you can think of now, this habit of listening will protect you from danger.

The Germans have a proverb, "Hear much and say little." What does it mean?

III. SEEING AND READING

You can learn a great deal through your ears, but think how much more you can learn through your eyes. Just count over all the things that you have had to get your eyes to tell you to-day, and then shut your eyes for a minute and think what it would mean never to be able to see. Don't you think you ought to take very good care of your eyes? You are going to keep them very busy all your life, and they deserve the very best care you can give them.

Just as soon as lessons begin, you get out your books; and a good share of the day in school you have a book before you, reading it or studying it or copying from it. It makes a great difference to your eyes how you hold the book and how the light falls. In reading, you should always hold your book so that the light falls upon the page from behind you, or from over one of your shoulders. In this way, the brightest light that comes into your eyes is not from the window, but from the page of your book.

If the light comes from a window in front of you, or if you sit in the evening with your face toward the lamp when you read, the light coming straight from the lamp or the window, as well as the light coming up from the pages of the book, pours into your eyes; and this dazzles and confuses your eyes, so that you can't see plainly and comfortably and are very likely after a while to find that your head aches. At home, of course, you can seat yourself with your back to the light when you read; and usually at school your seats are so arranged that the light falls from behind you or from one side. If not, by turning a little in your seat, you can get the light from over your shoulder.

Notice how the light falls upon the blackboard. When the light comes from the windows behind you, or from one side, you can see what is written there quite plainly. But if the blackboard happens to be between two windows, and especially if this is the lightest side of the room, you will find that the light dazzles you so that you cannot see the writing clearly.

You must have noticed, too, that if, after you have been reading from the blackboard you look down again suddenly to the page of your book, for an instant you will not see the letters plainly. Then, almost before you have time to notice it, you feel a little change take place inside your eyes, and the print upon the page of your book becomes quite plain. This is because your eye has to change the shape of one of the parts inside it, called the lens, before you can see clearly the things that are near you. This change, which is called accommodation, is made by a little muscle of the eye; and if you keep your eyes working at close work, like reading or writing or fancy-work, too long at a time, or if your eyes need glasses to make them see clearly, and you haven't them on, this little muscle becomes tired. Then the print of your book, or your writing, or the stitches you have taken begin to blur before your eyes. Your eyes begin to feel tired, and your head begins to ache. This is what we call eye strain.

Sometimes this eye strain upsets your appetite or your digestion and makes you sleepless and worried. The trouble may be caused by your own carelessness: you may have been reading too long, or in a poor light, or with the light shining right in your face instead of coming over your shoulder. But sometimes it is caused by the fact that your eyes are not just the right shape; and then the only way to relieve it is to have proper glasses, or spectacles, fitted, which will make up for this too flat or too round shape, or too large or too small size, of your eyes.

If you cannot see clearly what is written on the blackboard when the light falls upon it from behind you, or above; or if, in a good light, you cannot read the words in your book quite easily, without straining at all, when you hold the book either at arm's length or a foot from your face; or if your head aches or your eyes begin to feel tired or uncomfortable, or the letters begin to blur, after you have read steadily--say, for half an hour,--it is a pretty sure sign that there is some trouble with your eyes. Then you had better have them examined at once by your family doctor or by the school doctor. In many schools now there are doctors to test the children's eyes, and ears, too, so that each child may have a chance to see and hear everything that the other children can see and hear.

Not very many years ago people thought that glasses were only for old people, but now we know that many children's eyes need glasses, too. I knew a little girl whose sight was so poor that when she was standing and looked down at the grass, she couldn't see the green blades. She thought that the grass looked like a green blur to everyone, just as it did to her; and so she never said anything about it. She was twelve or thirteen years old before she found out that she couldn't see clearly. Of course, trying hard to see things gave her a headache and made her tired and cross. So some one took her to a doctor, and he saw at once what was the matter and fitted her with glasses. Soon she was quite well and strong; and how glad she was to see the leaves and a hundred other things she had not seen before!

The muscle from M to M, which helps to turn the eyeball, has been cut away to show the optic nerve.]

Here we have a picture of the eyeball, as we call it. The little bands fastened to it are the bands of muscle; and as soon as I say muscle you know what they are for--to move the eyeball about, up and down and from side to side. There are muscles outside the eye as well as inside. Coming out from the back of the eyeball is a pearly white cord quite different from the muscle bands. This is what we call a nerve. This nerve in your eye carries to your brain, or thinking machine, picture-messages of whatever you look at.

The nerve in your eye gets messages of light much as the nerve deep in your ear gets its messages of sound--from tiny waves in the air. The light waves are smaller and faster even than the sound waves, and the eye nerve is the only nerve that can get pictures of them. You know that, for wireless messages, the receiving machines are not all alike and cannot all take the same messages, if the messages are sent with different sorts of electric waves; and neither can our receiving machines. Some get messages of sight, and some of sound, and some of touch, or taste, or smell.